Polyamide release film for use in the production of molded composite products

ABSTRACT

A film for adhering to a molding compound paste composite during its manufacture, said film being formed from a blend of a film forming polyamide resin and at least one release agent material selected from the group consisting of N, N′ ethylene bis amides of the formula: 
     
       
         R 1 —CO—NH—CH 2 —CH 2 —NH—CO—R 2 , 
       
     
     wherein R 1  is an aliphatic hydrocarbon chain of about 14 to about 42 carbon atoms, and R 2  is a hydrogen atom or an aliphatic hydrocarbon chain of about 14 to about 42 carbon atoms; calcium stearate; a mixture of calcium stearate and silicone; a mixture of calcium stearate and polytetraflurorethylene; polypropylene; modified polypropylene; waxes; fluoroelastomers; silicones; molybdenum disulphide; boron nitride; N, N′ ethylene bis stearamide and polytetrafluoroethylene; N, N′ ethylene bis stearamide and silicone; N, N′ ethylene bis stearamide and graphite; N, N′ ethylene bis stearamide and polypropylene; N, N′ ethylene bis stearamide and molybdenum disulphide; waxes and polytetrafluoroethylene; waxes and silicone; polytetrafluoroethylene and silicone; polytetrafluoroethylene and maleic anhydride modified polypropylene; silicone and graphite; silicone maleic anhydride modified polypropylene; calcium stearate and molybdenum disulphide; calcium stearate and boron nitride; calcium stearate and polytetrafluoroethylene; calcium stearate and graphite; waxes and maleic anhydride modified polypropylene; polytetrafluoroethylene and graphite; polytetrafluoroethylene, silicone, graphite and molybdenum disulphide or boron nitride; and molybdenum disulphide and boron nitride, with the proviso that any modified polypropylene present does not exceed 3% by weight and wherein the release agent material is present in an amount such that after the paste composite is formed, substantially all of the film can be removed from the surface of the composite.

RELATED APPLICATION

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/828,919, filed Mar. 28,1997 now U.S. Pat. No. 5,959,031,which claims priority to U.S. Provisional Applications No. 60/014,615,filed Mar. 29, 1996 and Ser. No. 60/017,564, filed May 14,1996.

FIELD OF THE INVENTION

This invention relates to polyamide film having improved slipcharacteristics suitable for use as a release sheet in the preparationof molding composites, such as sheet molding compound (SMC), thickmolding compound (TMC) and bulk molding compound (BMC) which aregenerally used in the manufacture of vehicle parts and components. Thesecomposites have other applications, such as in the manufacture ofplumbing fixtures, for example one-piece tubs, showers, hot tubs,whirlpools and the like.

BACKGROUND OF THE INVENTION

One of the major concerns of the motor vehicle industry is to producelighter weight, more energy and more cost efficient automobiles.Consequently, much work has been done to develop plastics withsufficient strength and durability to replace many of the metalcomponents of motor vehicles, including structural support parts. Areinforced plastic part must possess structural strength and integrityequivalent to a metal component while simultaneously reducing its weightat equal, or preferably, lower cost. Therefore, development of highstrength structural composites has been directed to upgrading moldingproducts such as SMC, BMC and TMC.

As mentioned previously, these composites have other applications andhave found utility in the commercial and domestic plumbing markets whereone piece shower and/or bath installations are produced which offerconstruction labour and cost savings.

SMC is a composite material and usually comprises crosslinkablepolymeric resin, most often unsaturated polyester resin; styrenemonomer, plus catalyst; particulate filler, such as calcium carbonate;chopped glass fiber reinforcement; and various other additives in minoramounts, such as pigments and other modifiers.

The manufacture of SMC begins by laying the paste comprising allingredients except the glass fibers, on a bottom carrier or releasesheet, i.e., a film. The glass fibers are poured on top of the resin.More paste is poured over the glass fibers. A top carrier release sheetis laid down, and the edges of the top and bottom sheets are folded overto form a sandwich. The film and hence the composite is then kneaded tomix the glass fibers and the paste. The sandwich is then festooned(folded back and forth in a continuous fashion) into a bin and storedfor up to about 14 days to cure or mature. Satisfactory results may beobtainable after as little as 2.5 days, but often more time is required.During this time the viscosity of the composite increases significantly(approximately ten fold).

At the end of the curing period, the carrier release films, top andbottom are stripped away, the solidified SMC is cut and put into aheated press. In roughly one minute or less, out comes a semi-finishedproduct, such as an auto part, for example, an automobile hood.

TMC is produced by a different machine and process than that used forproducing SMC. Although TMC is prepared as a continuous length ofmaterial, it is cut into slabs for curing and storage because it isthicker than SMC. SMC is usually 1″ thick, but may range from ¼″ to 3″in thickness. TMC may range from ½″ to 4″ in thickness. TMC is strongerbecause some of the fiberglass fibers may be positioned vertically, andmore filler may be added. A most significant difference between SMC andTMC is that in making TMC, the glass fibers are mixed with the pasteprior to being deposited on the carrier or release film, and thus nokneading of the composite sandwich is necessary when TMC is made intoslabs. This therefore places different requirements on the carrier orrelease film as tear strength may not be as critical for carrier releasefilm used to make TMC.

BMC is also a composite material of resins, fillers and reinforcements.Typically, it comprises 30% resins, 50% fillers and additives and 20%reinforcement, such as glass fiber. It may also contain catalysts. Thehigh filler loadings can provide improved stiffness and fire retardness.BMC is manufactured by preparing a putty-like molding compoundcomprising the above-noted components in a “ready to mold” form. Moldingpressures usually range from about 350 to 2000 psi at temperatures ofbetween 250 and 350° F. BMC can be added into precise shapes withvarious types of inserts, the moldings can be extremely complex. Onelimitation of BMC is the loss of strength caused by degradation of glassfiber reinforcements during energy-intensive mixing.

BMC is primarily used as a replacement for cast metals. The actualphysical characteristics of BMC are determined primarily by the choiceof resin and desired end use. Possible end uses include: electricalgrade; low shrink/general purpose; appliance/structural; low profile;automotive grade; and corrosion resistant. Major applications of BMCinclude: air conditioner components; pump housings; circuit breakers;computer and business equipment components; garbage disposal housings;motor parts; power tools; gear cases; electrical insulators; and circuitcovers.

In selecting a carrier release film there are some basic requirements orproperties that are preferably met for the film to be suitable. Whilestyrene barrier, moisture barrier, and mechanical strength are relevant,most important are release from the paste composite, be it SMC, BMC, orTMC, and the cost of the release film.

RELEASE FROM THE SMC PASTE

The film must release cleanly from the molded product surface. If any ofthe film is left behind this will affect the final painted finish of thesurface. The film must also not carry any of the paste as it is peeledaway from the molded surface. This is generally considered to be one ofthe most important, if not the most important, property for acommercially useful carrier release film. Typically, this film propertysignals that the film will exhibit an adequate level of the majority ofany of the other desirable properties for such films.

FILM PRICE

This property speaks for itself given that it is important to keep costsas low as possible and yet produce quality product. At the same time,since the film does not form part of the final product and is eitherthrown away or recycled, its cost is significant and efforts to keep itto a minimum are constant.

There have been a number of different types of films proposed for use asrelease films in the manufacture of molded composites. Examples includelow density polyethylene (LDPE), high density polyethylene (HDPE), alaminate of HDPE/Nylon/HDPE, nylon, polyvinylidene chloride andcellophane.

In U.S. Pat. No. 4,444,829, which issued Apr. 24, 1984 to Bollen,Degrassi and Sacks, there is described a low crystallinity polyamidefilm comprising a blend of 90 to 70 wt. % of a polyamide having acrystallinity of less than 35% and 10 to 30 wt. % of a polyolefincomponent. The polyolefin component, which is a linear high molecularweight polymer of alpha-olefins, copolymer of alpha-olefin and vinylacetate monomers or an alkyl acrylate, has a crystallinity of less than50%.

In Sipos' Australian Accepted Specification No. 628105, published Sep.10, 1992, there is claimed a film for use as a release film made from ablend comprising i) from 2 to 25 wt. % of a grafted terpolymer havingtwo of the three monomers selected from the group consisting of C₂ toC₂₀ alpha-olefins, and wherein the grafted terpolymer is grafted with agrafting monomer selected from the group consisting of acrylic acid,methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonicacid, 5-norbornene-2,3 dicarboxylic acid, methyl-5-norbornene-2,3dicarboxylic acid, maleic anhydride, dimethylmaleic anhydride,monosodium maleate, disodium maleate, acrylamide, itaconic anhydride,citraconic anhydride, maleimide, N-phenylmaleimide, diethyl fumarate,vinyl pyridines, vinyl silanes, 4-vinyl pyridine vinyltriethoxysilaneand allyl alcohol, ii) from 5 to 25 wt. % of a non-grafted terpolymerhaving two of the three monomers selected from the group consisting ofC₂ to C₂₀ alpha-olefins, iii) an aliphatic polyamide and iv) from 0 to25 wt. % an alpha-olefin polymer selected from the group consisting ofhomopolymers of ethylene, homopolymers of propylene, homopolymers ofbutene-1, copolymers of ethylene and a C₃ to C₁₀ alpha-olefin,copolymers of ethylene and acrylic acid, copolymers of ethylene andmethacrylic acid, copolymers of ethylene and vinyl acetate, andionomeric polymers derived from copolymers of ethylene and acrylic acidor methacrylic acid; said alpha-olefin monomers being present in thegrafted terpolymer and the non-grafted terpolymer in amounts of up to 80wt. % of the terpolymers; the total content of the alpha-olefin polymer,the grafted terpolymer and the non-grafted terpolymer being equal to orless than 30 wt. % of the blend, and the balance of the blend being analiphatic polyamide, the melt viscosities of said polyamide, terpolymerand grafted terpolymer being selected such that the blend ishomogeneous:

In Sipos' Australian Accepted Specification No. 621956, published Mar.26, 1992, there is claimed a release film made from a blend comprisingfrom 5 to 25 wt. % of a C₂-C₂₀ alpha-olefin polymer grafted with anethylenically unsaturated hydrocarbon with at least one functionalgroup, and from 95 to 75 wt. % of an aliphatic polyamide, the meltviscosities of said polyamide and graft polyolefin being selected suchthat the blend is homogeneous.

Calcium stearate is known as a processing aid for the manufacture ofresins and it is also known to be used as a metal mold release agent.However it has not been used as a release agent in release film used inthe manufacture of molding composites.

While there are commercial products that are currently used as a carrieror release films in this area, there remains a need for a carrier orrelease film which meets the above requirements to a greater extent,particularly if those films offer cost advantages.

SUMMARY OF THE INVENTION

The invention of U.S. parent application Ser. No. 08/828,919 filed Mar.28, 1998 claims a mold or release carrier film for use in themanufacture of molding compound composites formed from a blend of a filmforming polyamide resin and at least one release agent material selectedfrom the group consisting of

N,N′ ethylene bis amides of the formula:

R₁—CO—NH—CH₂—CH₂—NH—CO—R₂

 wherein R₁ is an aliphatic hydrocarbon chain of about 14 to about 42carbon atoms, and R₂ is a hydrogen atom or an aliphatic hydrocarbonchain of about 14 to about 42 carbon atoms.

The present invention provides a film for adhering to a molding compoundpaste composite during its manufacture, said film being formed from ablend of a film forming polyamide resin and at least one release agentmaterial selected from the group consisting of

N, N′ ethylene bis amides of the formula:

R₁—CO—NH—CH₂—CH₂—NH—CO—R₂,

 wherein R₁ is an aliphatic hydrocarbon chain of about 14 to about 42carbon atoms, and R₂ is a hydrogen atom or an aliphatic hydrocarbonchain of about 14 to about 42 carbon atoms;

calcium stearate;

a mixture of calcium stearate and silicone;

a mixture of calcium stearate and polytetrafluororethylene;

polypropylene;

maleic anhydride modified polypropylene;

waxes;

fluoroelastomers;

silicones;

molybdenum disulphide; and

boron nitride;

N, N′ ethylene bis stearamide and polytetrafluoroethylene;

N, N′ ethylene bis stearamide and silicone;

N, N′ ethylene bis stearamide and graphite;

N, N′ ethylene bis stearamide and polypropylene;

N, N′ ethylene bis stearamide and molybdenum disulphide;

waxes and polytetrafluoroethylene;

waxes and silicone;

polytetrafluoroethylene and silicone;

polytetrafluoroethylene and maleic anhydride modifiedpolytetrafluoroethylene;

silicone and graphite;

silicone and maleic anhydride modified polytetrafluoroethylene;

calcium stearate and molybdenum disulphide;

calcium stearate and boron nitride;

calcium stearate and polytetrafluoroethylene;

calcium stearate and graphite;

waxes and maleic anhydride modified polytetrafluoroethylene;

polytetrafluoroethylene and graphite;

polytetrafluoroethylene, silicone, graphite and molybdenum disulphide orboron nitride; and

molybdenum disulphide and boron nitride

with the proviso that any modified polypropylene present does not exceed3% by weight and wherein the release agent material is present in anamount such that after the paste composite is formed, substantially allof the film can be removed from the surface of the composite.

In another aspect, the invention provides a molded composite having amold release or carrier film adhered thereto, as described above.

This class of polyamide/amide films and their method of manufacture aredisclosed in U.S. Pat. No. 4,490,324 issued Dec. 25, 1984 to Mollison,the disclosure of which is hereby incorporated by reference. The amideis preferably present in the blend in an amount that will permit removalof substantially all of the film from the paste. In the referencedpatent, the amide may comprise from about 0.05 to about 1.0% by weightof the blend. Preferably, the amount used in the present blend issufficient to permit substantially all of the film to be removed fromthe composite. It may range from about 0.05 to about 10% by weight, morepreferably, the amount is from about 1.0% to about 3.0%. Most preferredis about 1.5% by weight of the blend.

In another preferred aspect, the invention provides a mold or releasecarrier film for use in the manufacture of molding compound compositesformed from a blend of a film forming polyamide resin and a materialcomprising either calcium stearate or a mixture of calcium stearate withsilicone or polytetrafluoroethylene.

In another aspect, the invention provides a molded composite having amold release or carrier film adhered thereto, wherein the film is formedfrom a blend of a film forming polyamide resin and a material comprisingeither calcium stearate or a mixture of calcium stearate with siliconeor polytetrafluoroethylene.

The calcium stearate preferably may be present in the blend in an amountin the range of from about 0.01 to about 5% by weight of the total blendcomposition, more preferably from about 0.1 to about 2% by weight, andmost preferably, the amount may be about 0.8 to about 1.2% by weight.

When the calcium stearate is used with polytetrafluoroethylene orsilicone, the calcium stearate may preferably range from about 0.01 toabout 5% by weight, while the polytetrafluoroethylene may preferablyrange from about 0.01 to about 5% by weight. The silicone when combinedwith the calcium stearate may be present preferably in the range of fromabout 0.01 to about 5% by weight, with the calcium stearate preferablybeing present in an amount within that range also. The narrower rangesfor calcium stearate also apply to the silicone andpolytetrafluoroethylene.

It is also possible to characterize the amount of calcium stearate asparts per million of calcium as determined by Neutron ActivationAnalysis (NAA), in which case the above ranges would be preferably fromabout 6.5 ppm to about 3300 ppm, more preferably from about 66 ppm toabout 1300 ppm, and most preferably from about 530 ppm to about 790 ppm.

Examples of the release agent for the polyamide resin are:

1% calcium stearate;

1% calcium stearate and 2.5% polytetrafluoroethylene; and

1% calcium stearate and 2% silicone.

The calcium stearate may be selected from any forms that arecommercially available in such a form for incorporation with thepolyamide. One example of a suitable form is that sold by The NoracCompany, Inc. under the trade-mark COAD 10B which is available in powderand a lower dusting granular form. It may be in the form of a powder,granules, beads, flakes or any other suitable form.

The polytetrafluoroethylene which may be used may also be anycommerically available form that is suitable for incorporation in thepolyamide and the other ingredients present in the blend. One example ofa suitable material is that sold by DuPont under the trade-mark TEFLON.TEFLON MP1300 and TEFLON MP1150 have been used successfully.

The silicone may also be selected from any commercially available formthat is suitable for incorporation with the polyamide and otheringredients present in the blend. One example of a suitable material isthat sold by Dow Corning Canada Inc. under the designation DOW CORNING®MB50-011. Typically a Master Batch comprising 50% Nylon 6 and 50%silicone is used. Dow Corning® provides pelletized micro-dispersions ofa special ultra-high-molecular-weight silicone polymer in variousthermoplastic carrier resins at loadings of up to 50 percent.

Dyes and/or pigments may be incorporated into the blend to facilitateseeing the film once applied to the composite. This helps with removal.Any dye or pigment which may readily be incorporated into the otherblend components may be used. BASF supplies a dye under the trade namePALAMID Yellow 15-605. This consists of a 75% Nylon 6 base and 25% of acolour load. BASF also supplies a suitable pigment under the designation21-0705. These have been found to be suitable for use in the resinblend.

In most preferred forms of the invention, the individual release agentsmay be used in combination in the amounts set out below.

TABLE I Preferred Amount Most Preferred Release Agent % by weight % byweight MZ109D maleic anhydride 2-3 2.75 modified polypropyleneCrodamide ® EBS Beads (fatty 1-2 1.5 acid amide) or Kemamide ® W40Epolene ® G-3003 wax maleic 2-3 2.75 anhydride modified polypropyleneLuwax ® OP Flakes montanic 0.5-1.5 1.0 acid ester waxes Dow CorningSilicones 1.5-2.5 2.0 Calcium Stearate 0.8-1.2 1.0 Viton ®(fluoroelastomers) 0.02-0.04 0.02 Teflon ® 1.2-2.0 2.0(polytetrafluoroethylene)

It is possible to use many different combinations of these release agentmaterials and the examples herein are merely representative of thevarious combinations possible.

In most instances a dye is added to the resin mixture in order for thefilm to be visible. Often this dye may be N6,6 yellow dye in a preferredamount of about 0.2 to about 0.3% by weight, more preferably about 0.2%by weight.

In the event these release agents are used individually, the preferredand most preferred ranges are as follows:

TABLE II Preferred Range Most Preferred Claimed in % Range in % ReleaseAgent by weight by weight N6,6 0.01-5.0 0.5-2.0 Crodamide ® EBS Beads orKemamide ® W-40 (fatty acid amide) Calcium Stearate 0.01-5.0 0.5-2.0 DowCorning Silicone Master 0.01-5.0 0.5-3.0 Batch Viton ®(fluoroelastomers) 0.01-4.0 0.01-2.0 N6,6 Yellow Dye 0.01-2.0 0.1-1  Teflon ® (polytetrafluroethylene) 0.01-5.0 0.5-3.0 Polypropylene0.01-3.0 1.0-3.0 Luwax ® OP Flakes BASF 0.01-5.0 0.5-2.0 montanic esterwaxes Epolene ® G-3003 Wax 0.01-3.0 0.5-2.0 (chemically modifiedpolypropylene 99.0 wt. %, 4.0 wt. % maleic anhydride) Fusabond ® MZ109DDuPont  0.1-3.0 1.0-3.0 maleic modified polypropylene

It s ould be noted that the commercial products mentioned above areexamples of commercially acceptable materials that fall within thegeneral classes of the various types of release agents.

The film blend may be made and then melt extruded into the film asdescribed in the above-referenced Mollison patent. However, the blend ispreferably made in one of two ways. The first method involves theaddition of the amide compound in the exact amount required for theformulation. The second method comprises combining pure polyamide resinwith a blend of the polyamide resin and the amide or other additives. Insuch instance, the amount of the blend combined with the pure polyamideis adjusted to provide the desired amount of amide in the final blend.In the Mollison process, the film is extruded and cast, and then it isheated to improve the slip characteristics. Typically this technique isused when the amount of amide is at the low end of the preferred range.Generally, at the most preferred levels of amide used in the film blendof the present invention, heating after casting and before storage isnot required. However, if an oriented film is used, heating would beused. It is also believed that the use of an oriented film would permitdown gauging the film thickness, and this could produce additional costsavings depending on the orienting cost. If the film is re-heated, it isgenerally heated from between about 80° C. to about 140° C.

The polyamide used may be selected from all film forming, meltextrudable Nylon resins such as Nylon 6,6, Nylon 6, blends of Nylon 6,6and Nylon 6 and copolymers of hexamethylene diamine adipate andγ-caprolactam. Copolymers containing up to 25% by weight γ-caprolactammay be used, as may copolymers of about 90% by weight hexamethylenediamine-adipate and about 10% by weight of γ-caprolactum.

In one of its most preferred forms, the film blend comprises Nylon 6,6and N,N′ ethylene-bis-stearamide.

The molded composites are preferably selected from SMC, BMC and THC.Other types of composites may be manufactured using this film given itsproperties and these will be apparent to the person skilled in the art.The formulations for such pastes are well known in the art, but in thefollowing Table I there are set out typical generic formulations usedfor BMC, SMC and TMC. These represent formulations used commercially forthe manufacture of such composites. Many other suitable formulations maybe used and the examples here are meant to serve as a guide to theperson skilled in the art.

In the subsequent Table III, there are set out typical aspects of thepaste mix processes used to make BMC, SMC and TMC composites. All of theabove formulations and processes may be used to produce the compositesof the present invention. Again, other methods in the art may be used tomake these composites, and these examples are meant to serve as a guideto the person skilled in the art.

TABLE III FORMULATIONS-BMC vs. SMC vs. TMC BMC SMC TMC (Bulk MoldingCompound) (Sheet Moulding Compound) (Thick Molding Compound) PARTS A″SIDE PARTS PARTS Polyester Resin* 75 Polyester Resin 65 Polyester Resin65 Thermoplastic* 25 Thermoplastic 35 Thermoplastic 35 Hold Release* 4.0Hold Release 3.5 Hold Release 3.5 Catalyst* 1.5 Catalyst 1.5 Catalyst1.5 Filler* 300 Filler 200 Filler 225 Glass Fibers-¼″* 10-20 GlassFibers-1″ 25-30 Glass Fibers 10-20 Wgt. % Added at Machine Wgt. % ½″-1″Wgt. % Added at Machine Thickening Agent* 1 “B” Side 18 Thickening Agent1 (Optional) (Thickening Agent (Powder) Dispersion)

TABLE IV BMC vs. SMC vs. TMC MIX PROCESSES BMC SMC TMC PASTE MIX BatchBatch and/or Continuous Batch PROCESS: In-Line MIXER TYPE Low IntensityHigh Intensity High Intensity (Plough Type) (Cowles Dissolver) (Cowlesor Low Intensity Dissolver) (Horizontal Plough or Double Planetary)GLASS LENGTH ¼″-½″ 1″ ½″-1″ GLASS % 10-20 20-60 12-25 PASTE VISCOSITIES200,00-4 mm 10,000-60,000 10,000-100,000 BROOKFIELD (CPS)

In another aspect, the invention provides an improved process forproducing sheet molding composites which comprises:

(a) casting a layer of heat-curable thermosetting resin, in fluid form,onto a continuously advancing polymeric film;

(b) introducing reinforcing material onto the advancing fluid layer;

(c) laying a polymeric film on the top surface of said reinforced fluidlayer thereby forming a sandwich composite;

(d) advancing said sandwich composite through a series of kneading andcompaction rolls; and

(e) winding the sandwiched composite into a roll for partial curing;

the improvement comprising using as the polymeric carrier or moldrelease film, a blend of a film-forming polyamide resin and amide insufficient quantity to permit substantially complete release of the filmfrom the composite.

In another aspect, the invention provides an improved process for makingthick molding composites, comprising

(a) introducing reinforcing material into a heat-curable thermosettingresin, in fluid form and mixing same until the material is mixed andwetted;

(b) casting a layer of said mixture onto a continuously advancingpolymeric film;

(c) laying a polymeric film on the top surface of said reinforcingmaterial-resin layer to form a sandwich composite;

(d) advancing the sandwich composite through at least one compactionroll;

(e) cutting the continuous lengths of the sandwich composite intolengths for partial curing;

the improvement comprising using as the polymeric carrier or moldrelease film, a film made from a blend of a film-forming polyamide resinand an amide in sufficient quantity of a material to permitsubstantially complete release of the film, from the molded composite.

In another aspect, the invention provides an improved process forproducing sheet molding composites which comprises:

(a) casting a layer of heat-curable thermosetting resin, in fluid form,onto a continuously advancing polymeric film;

(b) introducing reinforcing material onto the advancing fluid layer;

(c) laying a polymeric film on the top surface of said reinforced fluidlayer thereby forming a sandwich composite;

(d) advancing said sandwich composite through a series of kneading andcompaction rolls; and

(e) winding the sandwiched composite into a roll for partial curing;

the improvement comprising using as the polymeric carrier or moldrelease film, a blend of a film-forming polyamide resin and, insufficient quantity to permit substantially complete release of the filmfrom the composite, a material comprising either calcium stearate or amixture of calcium stearate with silicone or polytetrafluoroethylene.

In another aspect, the invention provides an improved process for makingthick molding composites, comprising

(a) introducing reinforcing material into a heat-curable thermosettingresin, in fluid form and mixing same until the material is mixed andwetted;

(b) casting a layer of said mixture onto a continuously advancingpolymeric film;

(c) laying a polymeric film on the top surface of said reinforcingmaterial-resin layer to form a sandwich composite;

(d) advancing the sandwich composite through at least one compactionroll;

(e) cutting the continuous lengths of the sandwich composite intolengths for partial curing;

the improvement comprising using as the polymeric carrier or moldrelease film, a film made from a blend of a film-forming polyamide resinand a sufficient quantity of a material to permit substantially completerelease of the film from the molded composite, and selected from eithercalcium stearate or a mixture of calcium stearate with silicone orpolytetrafluoroethylene.

The film of this invention offers excellent release properties at alower cost than comparable films in the marketplace. The amide componentalso appears to act in an antistatic manner which therefore eliminatesthe need for the addition of antistatic material to the film blend.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings which are used to illustrate but not limitthe present invention,

FIG. 1 is a schematic illustration of a conventional apparatus andprocess used for the manufacture of SMC; and

FIG. 2 is a schematic illustration of a conventional apparatus andprocess used for the manufacture of TMC.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The film of the present invention can be prepared by thoroughly blendingtogether the main components and preferably a minor amount of a dyewhich allows the film to be seen easily once applied to the paste, andhence readily removed therefrom, followed by hot melt extrusion.

The film obtained from the present blend has a high gloss which makes itquite visible on a coloured paste. To improve the ability to see it, apigment may be added. A preferred pigment is PALAMIDE YELLOW which ismade by BASF. Typically it can be used in an amount of from about 0.1 toabout 0.5% by wt. based on the total weight of the blend, althoughpreferably it comprises about 0.2% of the blend.

Representative examples of suitable blending devices for forming theblend include drum tumblers, Banbury mixers, twin screw extruders, andheated roll mills. The temperature of the blending step is usually aboutambient temperature. The blend is then charged into a hot melt extruderequipped with a film—forming die, and the resulting film having athickness of up to 2 mils, preferably from about 1.0 mil is cast, cooledand may be rolled for storage.

A general description of the process for producing SMC is obtained byreferring to FIG. 1. Storage rolls 10 release stored film 12 ontocarrier/conveyor rolls 13 which transport the subject film 12 throughoutthe sandwich-forming process. Dispensers 14 deposit fluid SMCresin/filler paste 15 onto film 12 forming resin filler layer 16. InFIG. 1, to the bottom layer 16, glass reinforcement is added wherebycontinuous strand roving 17 is guided and advanced by roller 18positioned in relation to cutter 19 such that the roving strand 17 ischopped into smaller size reinforcing pieces 20, of about 1′ in lengthwhich are then deposited onto layer 16 of the advancing coated film. Thelayered film is collected on mandrel 23 to form a roll of SMC sandwichcomposite.

The above-described embodiment is a conventional method of producing SMCsandwich composite, in which the carrier film has been preformed in aseparate step, stored, and is then removed and used in the process. Analternate process would be where the film is produced in two differentfilm extrusion/casting operations and utilized directly to make SMCsandwich composite.

Another example of a typical SMC compound used to produce automotiveparts generally contains the following components; resin—formed from (1)unsaturated acids or acid anhydrides such as fumaric acid and/or maleicanhydride combined with (2) saturated acids or acid anhydrides such asphthalic anhydride and/or isophthalic acid or adipic acid reacted with(3) glycols or diglycols such as ethylene glycol, propylene glycol,diethylene glycol or dipropylene glycol; crosslinking monomer such asstyrene or vinyl toluene; catalyst—peroxides or per acids such ast-butyl per benzoate; catalyst activator—metallic soaps such as zincstearate; mineral extenders or filler—e.g. calcium carbonate;pigment—e.g. iron oxide; and thickening agent—e.g. magnesium hydroxide.An example of the amounts of these components is:

resin and monomer 100 parts catalyst 1 part catalyst activator 3 partsfiller 150 parts pigment 3 parts thickening agent 3.8 parts

To this resin mixture, chopped glass fiber, of about 1 to 2 inches insize, and/or other fibrous reinforcements such as carbon or metal fiberare added.

Referring now to FIG. 2 of the drawings, there is shown a schematicdrawing of a TMC process. Strands of fibreglass 51 are fled to a cuttingroller assembly 52 and 53, and the chopped fibreglass 54 is fed into akettle 50 which empties between a pair of rollers 57 to which a feed ofresin compound (not shown) is combined with the chopped glass at 56.Rollers 65 are wiping rollers for rollers 57 and these help direct themixture of resin and glass onto a lower carrier film 66 which feeds offa supply roll 58 and up onto a feeder roller 68. A set of lower feedrollers 63 and 62 and a belt 69 receive and feed the lower carrier film66. Nip roller 61 is in position to feed an upper carrier film 67 overthe top of the resin and glass mixture and to start compressing themixture between the upper and lower films 67 and 66, respectively.Compaction rollers 62, compress the long sandwich composite of thickmolding compound which is then fed off to be cut into suitable lengthsfor storage and shipping.

The following examples are illustrative of the best mode of carrying outthe invention as contemplated and should not be construed as beinglimitations on the scope or spirit of the instant invention.

EXAMPLES

The following resin formulations were prepared in accordance with thepresent invention.

TABLE V EXAMPLE No. COMPONENT % BY WEIGHT 1. Nylon 6,6 97.8 CalciumStearate 1.0 MB50-011 (Dow Corning) 1.0 Nylon 6 Yellow Dye 0.2 2. Nylon6,6 95.8 Calcium Stearate 2.0 MB50-011 2.0 Nylon 6 Yellow Dye 0.2 3.Nylon 6,6 96.8 Calcium Stearate 1.0 MB50-011 2.0 Nylon 6 Yellow Dye 0.24. Nylon 6,6 98.0 Calcium Stearate 0.8 MB50-011 1.0 Nylon 6 Yellow Dye0.2 5. Nylon 6,6 97.0 Calcium Stearate 0.8 MB50-011 2.0 Nylon 6 YellowDye 0.2 6. Nylon 6,6 97.8 Calcium Stearate 2.0 Nylon 6 Yellow Dye 0.2 7.Nylon 6,6 98.8 Calcium Stearate 1.0 Nylon 6 Yellow Dye 0.2 8. Nylon 6,698.44 Calcium Stearate 1.36 Nylon 6 Yellow Dye 0.2 9. Nylon 6,6 96.3Calcium Stearate 1.0 TEFLON 2.5 Nylon 6 Yellow Dye 0.2 10. Nylon 6,694.0 Calcium Stearate 0.8 TEFLON 5.0 Nylon 6 Yellow Dye 0.2 11. Nylon6,6 96.5 Calcium Stearate 0.8 TEFLON 2.5 Nylon 6 Yellow Dye 0.2 12.Nylon 6,6 100

PROCEDURE FOR SHEET MOULDING COMPOUND RELEASE TEST INTRODUCTION:

This test simulates the stripping of film from partially cured SMC as ina commercial process. Small strips of film are laid on SMC paste for aset duration. At the end of a set duration, the force required to removethe film from the paste is measured and recorded. The force provides aquantitative measure of the relative ease of different films for releasefrom SMC paste.

DESCRIPTION OF PROCEDURE

The first item needed is a metal tray with 0.5 inch sides. The tray canbe of any convenient size and made of an inexpensive material such asaluminum. The tray is lined with a polyethylene film, typically 1.5 milthick or thereabouts. At the end of the test, once the paste ispartially cured, the liner and the paste can be easily removed from thetray and the tray reused.

The tray is filled with prepared or mixed paste to about ⅜ inch deep.The paste should be fresh to replicate as best as possible, thecharacteristics that it would have in actual production on a commercialline. All ingredients, except glass fibers, should be present in thepaste in the ratio that is used on the commercial line. The paste shouldbe made up according to the mixing instructions provided by themanufacturer. Level the paste by agitating the tray. In pouring thepaste, ensure that no air bubbles are trapped.

On top of the paste, lay a Nylon film that has had 1 inch by 6 inchopenings cut into it. The openings are best cut with a NAEF type die inorder to achieve the same dimensions for each opening. Typically, theopenings are cut into columns and are equally spaced. The film shouldfit the tray tightly to prevent loss of styrene from the paste andpremature hardening. The film thickness is typically 1.5 mils.

From the films to be tested for release, at least two specimens of size1.5 inches wide by 8 inches long are cut. The specimens are laid on thepaste that is presented by the openings in the Nylon film. The specimensare placed on the paste and then lightly pressed to ensure that there iscomplete contact between the paste and the corresponding area of thespecimen. Any air should be removed. The intent is to ensure that thesurface of the specimen is well wetted with paste throughout the 1 inchby 6 inch opening but nowhere else.

The tray and film specimens sits for a duration of time that is decidedby the analyst. Usually it sits for the same length of time that is usedin the commercial process to cure the past before stripping of the film.Typically, this can be anywhere from 2 to 14 days. During this time, thetray should reside in a fume hood at room temperature (23° C.). The fumehood is needed to carry away any fugitive emissions of styrene.Variations in temperature could bias the procedure since the paste willnot cure properly if it sees temperature above or below roomtemperature.

The specimens are removed from the paste using a pneumatic or cross armpiston. Attached to the free end of the piston or cross arm is acalibrated instrument capable of measuring force. The preferredinstrument is provided by N. Zivy & Co. (Basle, Switzerland) and iscommonly called the “Zivy meter” or Instron Tensile Tester. Thepneumatic piston or cross arm is lined up with the centreline of thespecimen. The specimen is manually pulled back to expose ¼ inch to ½inch of paste so as to initiate the stripping of the film. The leadingedge of the specimen is clamped with a ¾ inch wide Binder Clip (orsometimes called a fold back clip). The Binder Clip is attached to thearm of the Zivy meter by a string. The piston or cross arm is locatedfar enough away so that the string shows no slack but neither is ittaut. The piston or cross arm is also positioned vertically so that thespecimen will be pulled through a tight hairpin turn of 180 back uponitself or alternatively at 90° to the paste. The piston or cross arm isactuated and the reading on the Zivy meter is recorded. Usually, themeter “spikes” at the start of the pull but quickly settles to aconstant value. This plateau is recorded and is deemed to be the releasetension of the specimen. In cases where the reading is variable, anaverage is taken. This most often occurs when the release of the filmfrom the paste is poor. The air pressure to the piston is set so that itretracts at the rate of 1.8 inches per second.

Once all the specimens are pulled, the amount of residue on surface ofeach specimen is qualitatively ranked and recorded.

This test is most efficacious when a number of control films is includedin the test. The control films are known to work satisfactorily in thecommercial process and provide a calibration between this test andfunctionality in the commercial line.

In the following Table VI, there are the results of paste release testsconducted in respect of the resins set out in Table V as well as Nylon6,6 on its own and a product that has been made by DuPont Canada for useas a mold release film. These results show that the film of the presentinvention performs at least as well as the DuPont Canada product whichwas perceived to have good commercial utility.

TABLE VI RELEASE TENSION (3 DAY PASTE TEST) EXAMPLE NO. FILM DESCRIPTION(GRAMS) 1. Nylon 6,6 and 1.0% calcium stearate 8,7,15 and 1.0% DowCorning MB50-011 and 0.2% Nylon 6 Yellow Dye 2. Nylon 6,6 and 2.0%calcium stearate 10 and 2.0% Dow Corning MB50-011 and 0.2% Nylon 6Yellow Dye 3. Nylon 6,6 and 1.0% calcium stearate 5,5 and 2.0% DowCorning MB50-011 and 0.2% Nylon 6 Yellow Dye 4. Nylon 6,6 and 0.8%calcium stearate 12 and 1.0% Dow Corning MB50-011 and 0.2% Nylon 6Yellow Dye 5. Nylon 6,6 and 0.8% calcium stearate 13,15 and 2.0% DowCorning MB50-011 and 0.2% Nylon 6 Yellow Dye 6. Nylon 6,6 and 2.0%calcium stearate 50* 0.2% Nylon 6 Yellow Dye 7. Nylon 6,6 and 1.0%calcium stearate 15,10,15 0.2% Nylon 6 Yellow Dye 8. Nylon 6,6 and 1.36%calcium stearate 7 0.2% Nylon 6 Yellow Dye 9. Nylon 6,6 and 1.0% calciumstearate 15,8,15 and 2.5% TEFLON and 0.2% Nylon 6 Yellow Dye 10. Nylon6,6 and 0.8% calcium stearate 8 and 5.0% TEFLON and 0.2% Nylon 6 YellowDye 11. Nylon 6,6 and 0.8% calcium stearate 12,10,7 and 2.5% TEFLON and0.2% Nylon 6 Yellow Dye 12. (control) Nylon 6,6 75,30,45 13. DuPontCanada Grafted polypropylene-polyamide 5,5,5,4,3 Commercial Resin resinmade in accordance with SIPO'S Australian Publication No. 621956 *Feeding problems at extruder. Sample contained possibly no calciumstearate.

The following examples are illustrative of the invention as contemplatedand should not be construed as being limitations on the scope or spiritof the instant invention.

EXAMPLES

In the following examples, comparisons were made among the release filmof the present invention and two other release films that have been usedcommercially. In each instance, the property measured is ReleaseTension.

TABLE VII Ex- Release Tension am- Film Film (5 day paste test) pleDesignation Description (grams) 1 DUPONT Grafted polypropylene- Average(2 films) = 16 S-701 polyamide resin made in Range = 10-22 accordancewith SIPOS' Australian Publication No. 621956 2 Conventional Nylon 6 andAverage (2 films) = 27 Commercial EVA (ethylene-vinyl Range = 12-40Product acetate) 3 Film of Present Nylon 6.6 and Average (2 films) = 14Invention 2% Kemamide W-40* Range - 10-18

TABLE IX Release Tension Release Tension Film Film (grams) (grams) Eg.Designation Description (2 day paste test) (5 day paste test) 1 DUPONTS- (see previous 11, 20 17, 20 701 description) (2 film strips tested)(2 film strips tested) 2 Conventional Nylon 6 and 10, 12 19, 20Commercial EVA (ethyl- (2 film strips tested) (2 film strips Product enevinyl tested) acetate blend) 3 DUPONT Nylon 6.6 21, 16, 25 21, 22, 43*EN707 and 1.0% (3 film strips tested) (3 film strips (film of Kemamidetested) invention) W-40 4 DUPONT Nylon 6.6 20, 20, 10 20, 22, 20 EN706and 1.5% (3 film strips tested) (3 film strips (film of Kemamide tested)invention) W-40 *Film specimen when laid on paste developed a deepcrease that impeded removal during testing.

METHOD

The test method is set out previously. The Kemamide containing films ofthe present invention contained BASF blue dye at the nominal level ofabout 0.25% by weight. The paste upon which these films were tested is atypical commercially available paste formulation used to make SMCcomposites.

DISCUSSION

The release tension results are consistent for the two tests conductedas set out in Tables VIII and IX. The DUPONT S-701 film performedconsistently in each test. While the release tension for theconventional commercial product is lower in Table IX, the range is notdissimilar to that observed in the test of Table VIII. The films of thepresent invention provided consistent results.

It should be understood that the detailed description and specificexamples which indicate the presently preferred embodiments of theinvention are given by way of illustration only since various changesand modifications within the spirit and scope of the appended claimswill become apparent to those of ordinary skill in the art upon reviewof the above description.

The following is a description of the Hand Sample Release Tests, theresults for which appear in the preceeding table.

Hand Sample Release Test Procedure

a) cut a 12″×12″ sample of film and fold it in half

b) lay a thinner layer of paste on one third of the film starting at thefold line

c) fold the film over the paste to create a sandwich

d) fold the free edges under the sample

e) cure the paste and film sandwich for 2-3 days

f) unfold the edges of the film

g) pull back the film on the top side of the paste

h) rate the sample subjectively against a control sample

The control sample, Example 10 is assigned a release tension value of10. Any film that displays a tension of less than 10 performs well.

In the following Table X there are examples of a number of filmformulations which illustrate combinations of release agents inaccordance with the present invention.

TABLE X Instron Test Film Description and Release Hand Sample ExamplePercentage by Weight Tension Release Test No. of Additive (g) ResidueRelease Residue 1. N6,6 (95.78%) 5, 8 less 10, 8 less MZ109D (2.5%) 7.5,7 less 7, 11 less Crodamide ® EBS 8 same 12 more Beads (1.5%) N6 YellowDye (0.2%) Viton ® (0.02%) 2. N6,6 (95.53%) 6 less 12 less MZ109D(2.75%) 5 less 11 less Crodamide ® EBS 12 same 11 slightly more Beads(1.5%) N6,6 Yellow Dye (0.2%) Viton ® (0.02%) 3. N6,6 (95.53%) 7 signif-8 less icantly less Epolene ® 7 less 9 less G-3003 Wax (2.75%)Crodamide ® EBS Beads (1.5%) N6,6 Yellow Dye (0.2%) Viton ® (0.02%) 4.N6,6 (96.03%) 5 same 8 slightly more MZ109D (2.75%) 6 same 9 more LuwaxOP ® 2 same 7 same Flakes (1.0%) N6,6 Yellow Dye (0.2%) Viton ® (0.02%)5. N6,6 (96.03%) 5 slightly 8 more more Epolene ® G-3003 Wax (2.75%) 6same 9 more Luxax OP ® Flakes (1.0%) 2, 2 same 8 same N6,6 Yellow Dye(0.2%) Viton ® (0.02%) 6. N6,6 (94.03%) 6 more 8 more Dow CorningMB50-011 slightly more Silicone (2.0%) 6 same 10 MZ109D (2.75%) 8 same12 slightly more Luwax OP ® Flakes (1.0%) N6,6 Yellow Dye (0.2%) Viton ®(0.02%) 7. N6,6 (94.03%) 5 same 8 slightly more Dow Corning MB50-011Silicone (2.0%) 6.5 same 9 more Epolene ® slightly more G-3003 Wax(2.75%) 5 same 7 Luwax OP ® Flakes (1.0%) N6,6 Yellow Dye (0.2%) Viton ®(0.02%) 8. N6,6 (95.87%) 8 slightly more 8 more Dow Corning EPA-25(1.66%) 4.5 same 11 more MZ109D (1.25%) Luwax OP ® Flakes (1.0%) N6,6Yellow Dye (0.2%) Viton ® (0.02%) 9. N6,6 (95.62%) 10 less 8 same DowCorning EPA-25 (1.66%) 5.5 same 12 more Epolene ® G-3003 Wax (1.5%)Luwax OP ® Flakes (1.0%) N6,6 Yellow Dye (0.2%) Viton ® (0.02%) 10.Grafted poly- 7 lots 10 slight (control propylene polyamide sample)resin made in accordance with SIPOS' Australian Publication No. 621956 7lots 10 lots none 10 none 11. N6,6 (98.8%) 4 less 8 less CalciumStearate (1.0%) 8 less 8 less N6,6 Yellow Dye (0.2%) 12. N6,6 (98.3%) 5less 8 less Crodamide EBS Beads (1.5%) 6, 5.5 less 8 less N6,6 YellowDye (0.2%) 4 more 11 more 13. N6,6 (94.53%) 3 same 10 same Luwax OP ®Flakes (1.0%) MZ109D (2.75%) Crodamide ® EBS Beads (1.5%) N6,6 YellowDye (0.2%) Viton ® (0.02%) 14. N6,6 (94.53%) 3 same 9 same Luwax OP ®Flakes (1.0%) Epolene ® G-3003 Wax (2.75%) Crodamide ® EBS Beads (1.5%)N6,6 Yellow Dye (0.2%) Viton ® (0.02%) 15. N6,6 (92.03%) 8 slightly 11slightly more more Epolene ® G-3003 Wax (2.75%) Crodamide ® EBS Beads(1.5%) Luwax OP ® Flakes (1.0%) N6,6 Yellow Dye (0.2%) Viton ® (0.02%)Dow Corning MB50-011 Silicone (2.5%) 16. N6,6 (92.03%) 5 more 12slightly more Luwax OP ® Flakes (1.0%) Dow Corning MB50-011 Silicone(2.5%) MZ109D (2.75%) Crodamide ® EBS Beads (1.5%) N6,6 Yellow Dye(0.2%) Viton ® (0.02%) 17. N6,6 (91.53%) 10 slightly 12 slightly moremore Luwax OP ® Flakes (1.0%) Dow Corning MB50-011 Silicone (2.5%)MZ109D (2.75%) Crodamide ® EBS (1.5%) N6,6 Yellow Dye (0.2%) Irganox1010 (0.5%) Viton ® (0.02%) N6,6 is Nylon 6,6

In the following Examples, there are described the preparations of filmsusing different release agent materials:

RELEASE FILM SCOUTING WORK

PHASE I

Fabricated approximately 36 different samples and controls. The sampleswere made by melt blending Nylon 6,6 with test ingredients in a able-topextruder and pressing the blended polymer into a thin flat sample (3 to5 mil) approximately 4 inches in diameter. The samples were made from ablend of 2% to 10% in the base resin. The samples were all tested withfive different adhesive systems.

a) Super Glue (#8 LePage)

b) Polymer Foam (“Great Stuff”)

c) Contact Adhesive Label

d) Contact Cement (#6 LePage)

e) A Commercial Composite Molding Paste (one of many)

The ease of release was rated for each system and an overall rating madefor each sample. The release from any of these materials is consideredto be predictive for release from composite molding paste.

Results indicated the following materials to be above average: EBS/W40;Luwax OP; Teflon; silicone; graphite; Sax 7429; calcium stearate;molybdenum disulfide and boron nitride.

The compounds that tested above average were selected for furthertesting by cross-compounding each with the others in a systematic testplan using the same procedures as above.

The best release results were not universal, but appeared to be specificto one or two adhesives. In order for a sample to be above average, itmust have tested high in release for at least two adhesive systems. Allthe samples were tested and rated and the overall score calculated.

The above average combinations were:

EBS/W40 and Teflon

EBS/W40 and silicone

EBS/W40 and graphite

EBS/40 and Sax 7429

EBS/40 and molybdenum disulfide

Luwax OP and Teflon

Luwax OP and silicone

Teflon and silicone

Teflon and Sax 7429

silicone and graphite

silicone and Sax 7429

calcium stearate and molybdenum disulfide

calcium stearate and boron nitride

calcium stearate and Teflon

calcium Stearate and silicone

Other combinations of merit for a single adhesive was:

calcium stearate and graphite

Luwax OP and Sax 7429

Teflon and graphite

The following combinations would reasonably be expected to give goodresults:

a) Teflon, silicone and graphite in combination with molybdenumdisulfide or boron nitride;

b) molybdenum disulfide mixed with boron nitride.

RELEASE TESTING PROCEDURES

a) Each sample was prepared by “gluing” two sample disks together.

b) Allowing a 48 hr. curing time.

c) Pulling the samples apart and comparing the force to a standard.

Pure Nylon 6,6 zero

The best sample in the series was rated 10 (near zero force)

All others subjectively rated 0 to 10

TABLE XI TABULATED RESULTS OF THE ABOVE AVERAGE TEST SAMPLES BlendedSuper Great Contact Contact SMC Ingredients Glue Stuff Adhesive CementPaste Calcium Stearate & 8 5 10 5-6 Teflon ® Calcium Stearate & 10 10-11N/a Moly-disulfide Calcium Stearate & 10-12 12 N/a Boron Nitride CalciumStearate & 10-11 N/a Graphite Calcium Stearate & 7-8 6-7 4 3-4 SiliconeEBS/W40** & 4 9 6 4 Teflon ® EBS/W40 & 6-7 10 N/a Graphite EBS/W40 & Sax8 7 4 7429 ®*** EBS/W40 & 9-10 9-10 5 4/6 Silicone EBS/W40 & Moly- 5 6-8N/a disulphide Luwax OP & 4/5 11 9 4 Teflon ® Luwax OP & Sax 6 8 7429 ®Luwax OP & 11 10-11 5-6 Silicone Teflon ® & Graphite 5-6 Teflon ® & Sax7 8-9 7429 ® Teflon ® & Silicone 5-6 10-11 Sax 7429 ® & 7 6 SiliconeSilicone & Graphite 8 10-11 Nylon 6,6 Control 0 0-2 0-1 0 2-3 S701****Control 5-7 5 2-3 1-2 5 Teflon ® Coated 10 13-14 5 10 4 Film Control -Nylon 6,6 Calcium Stearate 3-4 10 3 4 7 Control - Modified (propylene)Nylon 6,6 EBS/W40 Control- 6-7 6 4 0 3-4 Modified (propylene) Nylon 6,6*TEFLON is a registered trade-mark of E. I. duPont de Nemours andCompany for the product polytetrafluoroethylene. **EBS/W40 arecommerical names for ethylene bis stearamide each obtained from adifferent manufacturer. ***Sax 7429 is maleic anhydride modifiedpolypropylene. ****S701 is a nylon modified with polypropylene. Teflonwas incorporated in an amount of 5% by weight. All other release agentswere incorporated in an amount of 2% by weight.

The invention may be varied in any number of ways as would be apparentto a person skilled in the art and all obvious equivalents and the likeare meant to fall within the scope of this description and claims. Thedescription is meant to serve as a guide to interpret the claims and notto limit them unnecessarily.

What is claimed is:
 1. A film for adhering to a molding compound pastecomposite during its manufacture, said film being formed from a blend ofa film forming polyamide resin and at least one release agent materialselected from the group consisting of N, N′ ethylene bis stearamide andpolytetrafluoroethylene; N, N′ ethylene bis stearamide and silicone; andN, N′ ethylene bis stearamide and polypropylene; with the proviso thatany modified polypropylene present does not exceed 3% by weight andwherein the release agent material is present in an amount such thatafter the paste composite is formed, substantially all of the film canbe removed from the surface of the composite.
 2. The film as claimed inclaim 1 wherein the molded composite paste is selected from the group ofcomposites consisting of SMC, TMC and BMC.
 3. The film as claimed inclaim 1 wherein the polyamide is selected from the group of all filmforming, melt extrudable nylon resins.
 4. The film as claimed in claim 3wherein the polyamide is selected from the group consisting of Nylon6,6, Nylon 6, blends of Nylon 6,6 and Nylon 6, and copolymers ofhexamethylene diamine adipate and ε-caprolactam.
 5. A film as claimed inclaim 1 wherein the blend also comprises a dye in the amount of fromabout 0.1% by weight to about 0.5% by weight of the blend.
 6. The filmas claimed in claim 1 wherein the blend also comprises a dye in theamount of about 0.2% by weight of the blend.
 7. The film as claimed inclaim 1 wherein the release agent material comprises from about 1.0 toabout 5.0% by weight based on the weight of the blend.
 8. The film asclaimed in claim 1 wherein the release agent material comprises fromabout 1.0 to about 3.0% by weight based on the weight of the blend. 9.The film as claimed in claim 1 wherein the release agent materialcomprises about 2.0% by weight based on the weight of the blend.
 10. Afilm for adhering to a molding compound paste composite during itsmanufacture, said film being formed from a blend of a film formingpolyamide resin and at least one release agent material selected fromthe group consisting of N, N′ ethylene bis stearamide andpolytetrafluoroethylene, N, N′ ethylene bis stearamide and silicone; N,N′ ethylene bis stearamide and polypropylene.
 11. The film as claimed inclaim 10 wherein the release agent material comprises from more than 1.0to about 2.0% by weight, based on the weight of the blend.
 12. The filmas claimed in claim 10 wherein the polyamide is selected from the groupof all film forming, melt extrudable Nylon resins.
 13. The film asclaimed in claim 10 wherein the polyamide is selected from the groupconsisting of Nylon 6,6, Nylon 6, blends of Nylon 6,6 and Nylon 6, andcopolymers of hexamethylene diamine adipate and ε-caprolactam.
 14. Thefilm as claimed in claim 10 wherein the blend also comprises a dye inthe amount of ftom about
 0. 1% by weight to about 0.5% by weight of theblend.
 15. The film as claimed in claim 10 wherein the blend alsocomprises a dye in the amount of about 0.2% by wt. of the blend.
 16. Thefilm as claimed in claim 10 wherein the release agent material comprisesfrom about 1.0 to about 5.0% by weight based on the weight of the blend.17. The film as claimed in claim 10 wherein the release agent materialcomprises from about 1.0 to about 3.0% by weight based on the weight ofthe blend.
 18. The film as claimed in claim 10 wherein the release agentmaterial comprises about 2.0% by weight based on the weight of theblend.